Known spark-ignition (SI) engines introduce an air/fuel mixture into each cylinder that is compressed during a compression stroke and ignited by a spark plug. SI engines may operate in different combustion modes, including, by way of non-limiting examples, a homogeneous SI combustion mode and a stratified-charge SI combustion mode. SI engines may be configured to operate in a homogeneous-charge compression-ignition (HCCI) combustion mode, also referred to as controlled auto-ignition combustion, under predetermined speed/load operating conditions. HCCI combustion is a distributed, flameless, kinetically-controlled auto-ignition combustion process with the engine operating at a dilute air/fuel mixture, i.e., lean of a stoichiometric air/fuel point, with relatively low peak combustion temperatures, resulting in low NOx emissions.
Known plasma ignition systems may facilitate operation at lean air/fuel ratios, including operation in HCCI and other combustion modes. Known plasma ignition systems employ ignition plugs or igniters in place of spark plugs to ignite a fuel/air cylinder charge.